In a season-plus of watching Oregon practice behind closed doors, this was one of the most entertaining, sharp days I can remember, up there with the Alamo Bowl walk-through that convinced me the Ducks were going to beat Texas.

Both sides of the ball were very sharp against the scout teams, and then the day ended with a clutch period that included several highlight-reel moments. Yes, the Ducks were going to be heavy favorites regardless against South Dakota on Saturday (7:30 p.m. PT, Pac-12 Networks), but today they looked ready to take on all comers.

“We’ve been banging our heads on each other (for a month),” defensive end Arik Armstead said. “Saturday will be a good opportunity to hit somebody else besides your teammates. I think everybody’s going to unleash it. We’re looking forward to it and excited.”

Clutch began with the offense needing a touchdown, and Marcus Mariota quickly moved his group down the field. Passes to Thomas Tyner and Devon Allen, and a couple runs by Tyner, had the offense in striking distance. Mariota then found Allen in the end zone, and it looked like a sure touchdown – until the last second, when Reggie Daniels came flying from out of nowhere just in front of Allen to bat away the ball. Rodney Hardrick then broke up another pass, and the defense held.

The scenario was then changed to force the offense to drive to a field goal, but Mariota’s group did one better with a scoring drive capped by a Tyner touchdown run. The play concluded a very energetic, enthusiastic afternoon of work despite it being one of the hotter days of the month.

Highlights: An 11-on-11 period in the red zone featured an all-out assault on the end zone by Mariota’s group. Passes to Tyner, Keanon Lowe and Dwayne Stanford, runs by Tyner and Royce Freeman – it seemed like that group scored on nearly every rep. … On the defensive field, meanwhile, Tui Talia and Prevot forced an incompletion with their pressure, Joe Walker stuffed a running play, and Khalil Oliver hauled in a tipped ball for an interception. …

For the second straight day, the offense started really well in team situations. The first play of practice was a completion between Mariota and Lowe, who had a really nice connection going all day. A 7-on-7 period began with Allen getting behind the defense for a touchdown pass from Mariota. … Over on the defensive field during 7-on-7, Justin Hollins hauled down an interception. … During 1-on-1 passing drills in the red zone, Mariota had touchdowns to Lowe and Freeman, but was picked off by Erick Dargan. Dior Mathis and Arrion Springs had nice pass breakups. … I don’t want to overlook Byron Marshall, who also ran well in his reps with the ones. For the second practice since the Ducks released a depth chart with three potential starters at running back, it was impossible to tell from the sideline which might have the edge.

Other observations: Chris Seisay wore No. 12 rather than his usual No. 10 today, and the plan is for Hollins to wear No. 11 on Saturday. Seisay and the offensive No. 10, Loyd, figure to cross paths on the punt return teams at times, I’d assume; ditto Hollins and the offensive No. 31, Kenny Bassett, on the kickoff team. … It wasn’t a perfect day for the offense and defense. Among the highlights for the scout team, Jimmie Swain had a couple nice stops of Tyner and Freeman over the course of practice, and B.J. Kelley gave the secondary some trouble. Swain also switched fields and took some reps with the travel squad a couple times, backing up the notion he’s on the bubble to play this season if needed.